Photoelectric consistency indicating method



Feb. 5, 1946. D. L. WEST PHOTOELECTRIC CONSISTENCY INDICATING METHOD Filed June 23, 1941 3 Sheets-Sheet 1 INVENTOR ILLWfiST ATTOB Feb.5,19'46. 'D. L. WEST 2,394,129

PHOTOELEC IRIC CONSISTENGY INDICATING METHOD Filed June 23, 1941 3 Sheets-Sheet 2 INVENTOR ATTOB Y5 Patented Feb. 5, 1946 I UNITED srn'riszs PHOTOELECTRIO consis'rmvcy nv'mca'rmo METHOD Douglas L. West, MontreaL Quebec, Canada, as-

signor to Howard Smith Paper Mills Limited, Montreal, Quebec, Canada Application-lune 23,1941, Serial No. 399,364

'- In Canada June 6, 1941 -2 Claims. (Cl. 8814) This invention relates to improvements in methods adapted to be used for the purpose of indicating the consistency, turbidity, or other characteristics or properties of fluent materials such as aqueous suspensions of solids, solutions and the like. u

An important object of this invention is to Provide an improved method in which photoelectric cells are used in combination with a source of light and suitable indicating means for indicating'undesirable variations in the consistency of an aqueous suspension of solids such, for example, as a suspension of pulp fibres in water.

An important feature ofthe invention, as regards its use for indicating changes in the consistency or turbidity of suspensions or solutions resides in the provision of a. generally improved accompanying drawings. in which- ,Figure 1 is a view partl in front elevation and partly in vertical section of one form of instru- .method whereby those variations in the light the upwardly ment for use in performing the'method of my of part of a control Figure 4 is a wiring diagram of the electrical I device and connections embodied in'the instrument shown in Figure 1.

Figure 5 is a sectional "view ofa pilot valve forming part of said instrument.

Figure 6 is a sectional view of a'main valve forming part of said instrument.

to those changes in the light transmitting characteristics of the suspension which are due to changes in consistency. p

Unit l0 (see Figs. 1 and 3) comprises two cuprous oxide photo-electric cells l2 and I 3 arranged so that their light sensitive surfaces are exposed to light produced by a 250 watt Mazda flood lamp l4. This lamp is housed in the lower portion of a tubular lamp housing l5 and is positioned between oppositely located window openings l6 and 11. -A bico'nvex lens I8 is held in place over the window opening It by thehorizontal arm I! of an elbow 20 which is attached to the lamp housing so that its other arm 2| is directed upwardly. A reflecting mirror 22 is arranged in the elbow at an angle of to the central axes of the elbow arms l9 and 2|. Part of the light produced by the lamp it passes through the mated beam 23 which falls on the mirror 22 and is deviated 90 toward the bore of the upwardly directed elbow arm 2|. A casing 25 is mounted on the elbow 2. by a short length of tubing 26 having its upper end fastened to said casing and' I its lower end fastened to the upper extremity of directed elbow arm 2|. The top and bottom walls of casing25 are provided with glazed window openings 21 and 28 which are" aligned with each other and with the bore of the elbow arm 21. Casing 25 is also provided, for a purpose hereinafter set forth, with fluid inlet and outlet connections represented by the pipes v 29 and 30.

A cell housing 32 is mounted on cas ng 25 and contains the lightsensitive cell 12 whose light sensitive portion is exposed'to the light which is reflected'through the window open ngs 21 and 2! by the mirror 22, A light controll ng shutter ll is slidably mounted between the window openin 21 and thelightsensitlve portion of cell l2 and.

is adjustable to control the amount of lght'ialling on sald cell. As here shown the shutter 3.4

The instrument shown in Figs. 1 to 6 inclusive is especially adapted for indicating and controlling the consistency of an aqueous suspension such, for example, as a suspension of wood pulp fibres in water. It comprises an immersion or detecting unit I. and a combined indicating and control unit II. The unit in is immersed in the aqueous suspension as hereinafter described and serves to effect a predetermined operation of the indicating and controlllngunit II in response is provided with arack 35 which is driven by a to the lower end of an operatin pinion 3' fixed 21 extends'uowardly within a shaft 21. Shaft tubular extension II or housing 32 and is equippedat its upper end with a hand wheel 39. The ex-: end, as ind catedtension I8 is closed at'its upper at In. and is provided with a lateral opening ll through which the conductors 42 are passed to the cell l2. l I

The lamp housing its lower end and is provided at its upper end with a removable ca II which is secured in place by'a conventional arrangement of clamping bolts lens 18 and elbow arm l9- as a colli- I5 is permanently closed at The cell I3 is arranged in a housing 58 with its light sensitive surface facing a lens I fitted in the window-opening 52. The housing 58 is supported from the lamp housing I5 by a plurality of spaced supporting rods 53 so that the opposing lenses 49 and SI are separated by'a substantial space which, during use of 'the instrument, is occupied by a portion of the aqueous suspen sion A in which the unit I8 is submerged. The

conductors 55, connected to cell l3. are passed into housing 58 through a suitable conduit 56.

As shown in Figurel the lamp housing I5 is clamped; by U-shaped clamping bolts 58, to a thereby connect the pilot valve actuating coil 'II across the line wires 66 and 61. The deflection of the galvanometer needle in either direction also indicates on the calibrated galvanometer scale I8 (Fig. 1) the change in consistency re-- sulting in such deflection.

The pilot valve Illais shown in section in Fig. 5. It comprises a valve.I9 working in a liner 88 provided in a-valve casing 8|. Valve I9 is provided with an annular port '82 which is always in com munication with the valvecasing port 83 through saddle plate 59 rivetted to the inner end of a bracket 68 extending inwardly from one of the side walls of the flow channel 8| which, in the present instance, may be taken as representing a flow channel through which an aqueous suspension of wood pulp fibres indicated at A is being conducted to the flowbox of a pulp or paper making machine. The lamp housing I5 is clamped to the bracket 68 in such manner that the photo electric cells I2 and I3 and the lamp I4 are disposed .below the liquid level X.

A portion of the aqueous suspension A with which the flow channel 6| is supplied is filtered to separate the liquid from the solid component let pipes 38.

From the foregoing description it will be apparent that the amount of light received by the cell I2 is dependent ion the light transmittin properties of the flltrate'and the position of the light controlling shutter 34 while the amount of light received by the cell I3 is dependent on the density or consistency of the aqueous suspension flowing in the space between the lenses 49 and 5|.

It is important that the current supplied to the lamp l4 be maintained at a constant value. In the present instance the lamp is shownconnected across the secondary winding 63 of a 250 watt constant current regulating transformer 64 (see Fig. 4) whose primary winding 95 is connected across a 110 volt supply represented by the line wires 96 and 81. r

The combined indicating and control unit II comprises acontacting D. C. micro-amp central zero galvanometer 59 and a pair of pilot actuating coils I8 and II controlling the operation of a pilot valve Illa winch-in turn, controls the operation of a main hydraulic piston valve 12 which serves to open or close a water supply line I3 through which water is supplied to the aqueous suspension A to regulate the consistency thereof.

As shown in Figure 4 the photo-electric cells I2 and I3 are connected to the terminals of the galvanometer 59 and tend to cause the galvanometer needle 69a to be deflected in one direction or the other whenever there is uneven distribution of light between the cells. Deflection of the gal vanometer needle in one direction serves to close the control contacts I4 and I5 to thereby .con-

nect the pilot valve actuating coil 'I8acrossithe line wires 33 and 81 whereas an opposite deflection of the needle from a central zero point serves suitable openings 84 provided intermediate the length of the liner 88. Casing port 83 is located between an upper casing port 85 and a lower casing port 96. The upper casing port 85 is in communication with the upper openings 8'! of the liner 88 while the lower casing port 86 is in communication with the lower openings .89 of the liner 88. The casing port 83 is connected to a pressure fluid supply line 98 while the casing orts 85 and 83 are respectively connected, by pipe line's 9I and 92, to opposite ends of the cylinder 93 of the main valve 12. When the pilot valve I9 is .in the neutral position shown in Fig. 5, the valve casin ports 85 and 86 are isolated from the valve casing port 83.

' supplied, through pipe line 9|, to the left hand and the liquid component of the separation is continuously circulated through the casing 25 by means of the previously mentioned inlet and outend of the main valve cylinder 93 and acts against the piston 94 of the main valve 95 to move thevalve to the right. At this time fluid previously supplied to the main valve cylinder 93 through pipe line 92 is discharged through said pipe line to the casing port 86 of the pilot valve and passes from thence to the discharge pipe 95. When the pilot valve 19 is moved to its lowermost position the casing port 83 is connected to the casing port 88 so that pressure fluid now flows through pipe 92 to the right hand end of the main valve cylinder 93 and acts against the piston 91 to move the main valve 95'to the left, the pressure fluid previously supplied to the left hand end of the main valve cylinder 93 being now exhausted through pipe line 9|, pilot valve casing port and by-pass '98 to the exhaust line 96.

99 is provided, at one side of the partition I88,

with openings I84 communicating with chamber I82. Sleeve 99 is also provided, at the opposite side of partition I88, with openings I85 communicating with chamber I83. When the movable valve member is in the right hand or valve closing position shown in Fig. 6, the piston 94 blocks the openings I84 and disrupts communication between the chambers I82 and I83 thus preventing flow of fluid through the water supply line 13. When the pilot valve is in a position such that pressure fluid is supplied to the right hand side of cylinder 93 and exhausted from the left hand side of said cylinder, the piston 91 is forced to the left so that the piston 94 uncovers the openings I84 and permits flow. of water from the main valve chamber I82 to the main valve chamber I83. v

The movable valve member I9 of pilot valve 18a is connected by area I81 to a locking lever I88 which is intermediately pivoted at I89 to a Ill and H2 of the solenoid coils I and H are pivotally connected to thelever- 108 at oppositesides of the pivot I09 so that energization of the coil 10 serves to raise the pilot valve 19 to its uppermost position while energization of the coil 1| serves to lower the pilot valve to its lowermost position. The intermediately pivoted lever I08 is normally held in a horizontal position by means of suitable spring devices H3 and ill exerting downward pressure at opposite ends of the lever.

A pilot lamp I I5 is connected in the circuit shown in Fig. 4 so. that this lamp lights up whenever the pilot valve actuating coil is energized. A second pilot lamp] I6 is also connected in said circuit to light up whenever the pilot valve actuating coil II is energized.

In Fig. 1 the pilot lamps I I5 and Iii are shown mounted on a cabinet comprising atop compartment I ll containing the galvanometer 69 and a 3 the shutter 34 so that the amount of light falling on the cell i2 will be equal to the amount of light falling on the cell l3.

Assuming that the'shutter is adjusted to maintain equal disposition of lightsbetween the photoelectric cells l2 and ii for a given density or consistency of the aqueous suspension'A, it is obvious that any variation in the density .or consistency of the suspension will result in a corresponding variation of the amount of light falling on the cell i3 and will result in either a minus or plus deflection of the galvanometer needle de-, pending on whether the variation in the amount of light falling on cell It is due to an increase or decrease of density or consistency. When the vgalvanometer needle is deflected in response to a change in the consistency of the aqueoussuspension it acts, as previously explained, to energize one or the other of the solenoid coils "and II bottom compartment H8 which contains the transformer 64 and also supports the pilot valve actuating coils l0 and II and the pilot valve assembly 10a. The transformer 64 is equipped with'a series starting rheostat H9 (Figs. 1 and 4) which is adjusted by means of the operating knob I20.

The current transformer 64 may be of any suitable type but in the present instance I have shown a conventional constant current regulating transformer of the type in which the secondary coil 63 is suspended by a flexible counterhalancing weight system l2l so that it is free to move on the transformer coil I22. to maintain the current output of the transformer at a constant value. It is not considered necessary to enter into a detailed discussion of this type of-transformer since its operating characteristics are well understood in the art. It is sufllcient to state that the function of this transformer is to maintain constant current input to the lamp i4 against changes in the filament resistance of the lamp or variations of the line voltage applied to the primary coil 65 of the transformer. The object of such regulation is to preserve a constant brilliancy of light output from the lamp.

The purposejin circulating the filtrate through the casing 25, as previously explained, is to en'- sure that both cells l2 and I! will be equally affected by those changes in the light transmission characteristics of the aqueous suspension whichflare due solely to changes in the colour of the liquid components of the suspension and have no relation to the density or consistency chara'cror 22 by which it is reflected through the glazed window opening 28, the liquid in casing 25 and the glazed window opening 21 to fall upon the light sensitive surface of the cell l 2 It is obvious that if both photoelectric cells receive the same amount of light thereon, their voltages at the terminals of the galvanometer will balance .each

. other with the result that the galvanometer needle will remain at rest at the centre zero point of the scale I8. As the amount of light received' y the cell 13 is a variable-quantity,-dependent on-the density of the stock solution flowing between the lenses ll and II the galvanometer can be brought to balance for any density by adjusting to effect an appropriate operation of the main hydraulic valve I2 whereby the amount of water supplied to the suspension is increased or decreased as required.

The'instrument described herein has been found particularly useful for indicating and controlling the consistencyof dflute pulp stock suspensions whose desired consistency ranges from 0.25 to 8 or 9%. In this application of the invention the time response of the entire system is a factor of considerable importance. Wood fibres, even in a very dilute aqueous suspension, do not disperse evenly throughout a unit volume of the mixture.

Assuming all things to be constant, it may be stated that if such a suspension is traversed by light while it is in a flowing condition the light undergoe instantaneous changes of absorption corresponding to the variations ofdispersion ofthe wood fibres. As a result of this phenomenon the galvanometer needle varies between a plus and minus reading. It is therefore essential that the control afforded by the instrument described herein shall be based on an average condition of response and for this purpose the following conditions are necessary.

The light must be transmitted through as large a cross section of the suspension as is possible and this may be provided for by making the openings l1 and 52 and the lenses l9 and Ii as large as possible.

The system of the lens ll, mirror 22, fluid chamber 25, photoelectric cell l2 andshutter- 34 is providedfor obtaining galvanometer balance at zero -for some definite concentration of the aqueous suspension under test.- On the otherhand, since the two photoelectric cells l2 and l3 are connected in opposition at thegalvanometer, it will be apparent that any small variation of lamp brilliancy, which may be due to variations of the current supplied to the transformer and not being completely smoothed out will, upon reaching the photo cells as light fluctuations, be

cancelled out at the salvanometer asopposing voltages.

As regards the attainable sensitivity of control of the instrument, for a given galvanometer sensitivity,.thisis dependent on the optimum value of light which passes through the aqueous suspension from the lamp H. The greater this value, the greater will be the degree of galvanometer deflection as related to unit change of concentration of suspended solid matter. a I

As shown in Fig. -1,.the electrical connections to the cell l2-and the lamp H are encased in suitable conduits indicated at l 2|.

In Fig. 4 I have indicated how the valve oper claims.

ating motor I31 may be included in the electrical circuit so that its operation is controlled by the galvanometer 89.

Having thus described what I now consider to be the preferred embodiments of my invention,

' it will be understood that-various modifications may be resorted to within the scope and spirit material such as a solution or aqueous suspension which comprises connecting two photoelectric cells to operate an indicator in accordance with variations in the distribution of light between said cells, immersingboth cells in the fluid material under test to ensure that said cellswill be equally affected by changes in the temperature oi said material, directing a beam of light from a light source so that said beam traverses said fluid material and then falls upon the light sensitive surface of one of said cells, directing a second beam of light from the same light source so that said second beam of light falls upon the ligh;

sensitive surface of the remaining'cell without being passed through said fluid material and modifying the color characteristics oithe light falling upon the last mentioned cell to compensate for those color'changes which afiect the light transmitting properties of the fluid material but are not related to the turbidity or consistency characteristics of said material;

2. The, method recited in claim 1, in which the last mentioned step is accomplished by filtering a portion of the fluid material and passing the filtrate across the path of light from said light source to the last mentioned cell.

DOUGLAS L. WEST. 

